The present invention relates to scale inhibition in oil producing wells, in particular but not exclusively, sub-marine wells.
The formation of scale is a well known problem in oil production. As liquid is extracted from oil-bearing formations, mineral deposition occurs, principally sulphates and carbonates, particularly in the near-well-bore zone where higher liquid fluxes are experienced and also in the production equipment. Deposition of this scale occurs for a number of reasons, among which are pressure reduction, which affects various chemical equilibria, and the possible chemical incompatibility of the formation water and the water (usually treated seawater) pumped into the formations to replace the extracted material.
Scaling is usually combated using an inhibitor "squeeze", in which a material which inhibits the formation of scale is injected into the well-bore area via the production well. This means that production must be halted while the squeeze operation is carried out, which may take 24 to 48 hours. The costs involved, including the operation cost and lost production, may represent over 50,000 per squeeze, and each treatment tends to provide effective inhibition for about 6 months.